Could it be that the U.S. demand that's helped drive a near doubling of oil prices since mid-February was illusory? That may be a reasonable conclusion to draw from the latest data published by the country's Department of Energy.

The DoE, through the Energy Information Administration, produces two sets of U.S. demand data that drive sentiment and influence trading. The first shows monthly figures. They're two months out of date, but they give the most accurate assessment of what's going on in the world's largest oil-consuming country.

The second set of numbers come out each Wednesday, giving preliminary estimates for the previous week. For crude markets these weekly figures -- though less reliable -- are arguably more important, largely because they're bang up to date.

It's the discrepancy between the two sets of data that gives cause for concern.

When taking the weekly figures, it looks like U.S. gasoline demand is soaring. According to those data, it's been on a steady upward path all year, reaching a record high of 9.8 million barrels in the week ending June 17, with the summer driving season barely started. But the latest monthly data, showing the numbers for April, paint a very different picture.

Fantasy Driving?

Booming U.S. gasoline demand may be a figment of the imagination as monthly data show a slump

Sources: Bloomberg, EIA

They show U.S. gasoline consumption falling between March and April and imply a downward revision of April demand of 260,000 barrels a day, or 2.7 percent, from the preliminary figures. That might not seem a lot. But when the same agency forecasts that U.S. gasoline demand will grow overall this year by just 170,000 barrels a day, it's enough to change the whole outlook for one of the few countries where demand is robust.

The problem isn't confined to gasoline. According to the weekly numbers, overall U.S. oil demand has exceeded 20 million barrels a day in each of the past three months and, like gasoline, is on a steady upward path. Here, again, the monthly numbers show something very different. This time the revision is a whopping 800,000 barrels a day.

Disappearing Demand Surge

Surge in U.S. oil demand growth seen in weekly data disappears in more accurate monthly figures

Sources: Bloomberg, EIA

Strong U.S. oil demand growth, particularly for gasoline, has combined with supply disruptions in places like Canada and Nigeria to support the price rally. That recovery began in February when OPEC and other producers started talking about an output freeze.

The freeze never happened and the supply disruptions are easing. Canadian oil is coming back after the Alberta wildfires disrupted about 1.2 million barrels a day of production. The volume of output still shut in is now less than a third of the peak. Nigerian production is also returning, thanks to a ceasefire between the government and local militants.

So with the supply-side dynamics offering less of a prop to the crude price, more weight is being placed on demand. Yet analysts are becoming more pessimistic. Barclays has reduced its forecast of global demand growth this year to 1.1 million barrels a day from 1.2 million, after cutting its economic growth expectations because of the U.K. decision to leave the EU.

Last month, the World Bank lowered its forecast of global GDP growth in 2016 to 2.4 percent from 2.9 percent -- and that was before Brexit. With all this in mind, it's natural to look at the EIA's monthly U.S. data and wonder about the crude rally's robustness.

This column does not necessarily reflect the opinion of Bloomberg LP and its owners.